.btn {
    margin-top: 30px;
}

.flex_box {
    display: flex;
    width: 300px;
    height: 300px;
    box-sizing: border-box;
    border: 2px solid pink;
    border-radius: 10px;
    justify-content: center;
    align-items: center;
    margin-top: 20px;
}